The middle ear consists of the tympanic membrane (eardrum) 31 and three small bones, the malleus (“hammer”), the incus (“anvil), and the stapes (“stirrup”). When the small bones do not function properly, were damaged by a disease process, or were not formed properly during development, surgery can be performed to insert a middle ear prosthesis to replace or augment the bones.
However, when a patient undergoes middle ear surgery, a surgeon cannot generally tell how well the patient will hear after the surgery. Often, due to a variety of factors, the length of the middle ear prosthesis needs to be adjusted after the surgery. For example, each patient heals differently, and scar tissue forms differently, leading to a need for the length of the prosthesis to be adjusted.
Heinz-Kurz marketed the first titanium middle ear implant. These implants were originally produced as non-adjustable devices. This required storage and production of total ossicular repair prostheses (TORPs) and partial ossicular repair prostheses (PORPs) of a vast array of sizes to cover all possibilities for all patients. TORPs typically have a length in the range of 3 mm to 6 mm, and PORPs typically have a length in the range of 2 mm to 3 mm. The Heinz-Kurz prostheses were produced in sizes having lengths differing in increments of a quarter of a millimeter.
Spiggle & Theis introduced adjustable titanium middle ear implants in 1998. The heads of the implants were removable to allow the surgeon to manually trim the device to the desired length. Heinz-Kurz also produced adjustable implants. The TTPT™-VARIAC System of Heinz-Kurz includes a sizing disk that attaches to the prosthesis to assist in determining the fit for the patient. The sizing disk contains indentations with various depths to hold the prosthesis during the sizing procedure.
Currently, middle ear prostheses exist where the length of the prostheses can be shortened, such as those discussed above. When the length of one of these prostheses needs to be altered, the patient has another surgery and has the prosthesis removed. Once the surgeon removes the prosthesis, a shorter or longer prosthesis that is estimated to be the proper length is inserted into the patient. If the surgery is done under local anesthesia (i.e., the patient is alert), the patient then informs the doctor if he or she can hear better or not. If not, the process is repeated until the patient's hearing is satisfactory. Additionally, if during one of these iterations the patient had better hearing before the prosthesis was cut, that prosthesis is discarded and a replacement prosthesis of a longer length is inserted. If the surgery is done under general anesthesia (i.e., the patient is asleep), it is not possible to accurately predict the post-operative hearing result.
Thus, a middle ear prosthesis that is adjustable in situ and a method for adjusting a middle ear prosthesis in situ can reduce the number of surgeries patients need to have, the number of prostheses used, and/or allow accurate adjustment of the middle ear prosthesis.